Maryland Lake Water Quality

Maryland has 24 graded lakes in our dataset, sampled across 10 counties, drawing on monitoring by the Maryland Department of the Environment plus federal and volunteer measurements. A-grade lakes are scarce in Maryland: about 0% of the dataset. Most lakes here sit in C or D — productive, often shallow, frequently algal in late summer.

The state's dominant trophic class is oligotrophic: clear, nutrient-poor, slow-growing. These lakes are also the most sensitive to disturbance — the same volume that buffers them against nutrients also slows recovery if those nutrients arrive in quantity. a leading county ranks highest on average county grade (—). a struggling county sits lowest. With only 10 counties in the state, the cross-county spread is narrower than the within-county spread for most lakes.